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Hi yes
I got lent a pair of 4qds to use on the Wall/chimera they lasted one battle before the
circuit designated for the left side blew-I was using them on low ampage wheelchair
motors and I was dissapointed-guess they won't cope with bosche 850 or higher.
Save up and buy a roboteq or use home made relays is my advice.

They will do a good job but they are not robot friendly - you need a radio control interface as well as a controller for each side (they will only control one motor each) which adds up to a lot of expense and complexity, as well as space - a dual channel Vantec or something more modern like a Wotty will occupy less space, be simpler, and give you more current capacity - they also use a full H-bridge rather than relays to change direction (which my 4QDs have) so will be slightly more responsive as well.

Joey McConnell-Farber - Team Picus Telerobotics - http://picus.org.uk/
"At the point of the knife, you never see anyone, how the strong will survive, at the end of that gun...we run"

Hi, 4QD aren't the last word in controllers, but they are cheap and (pretty) reliable if mounted on a good heat sink. Have crude current limiting on them so don't go pop the first time a wheel jams. Lots of robots did really well with them in the past, and at least one I know swapped to them after finding Vantec unreliable. 4QD do an RC interface and mixing board to go with them too to give a three box solution

Main draw back - they are designed for golf buggies and wheel chairs so they have acceleration ramping which makes a robot easier to control but stops it reacting instantly (and going out of control). I don't believe that the ramping can be completely disabled. Though it's probably true to say that you would need to be a very good driver to be able to use the extra reactions of the robot instead of sending it into the pit!